1. Field of the Invention
Aspects of the present invention relate to a cognitive radio technology, and more particularly, to a technology to control a pilot signal power.
2. Description of the Related Art
Currently, much research on technologies to efficiently use limited frequency resources has been conducted. Among these technologies, a cognitive radio (CR) technology reuses frequency resources to efficiently use the limited frequency resources. That is, according to the CR technology, a communication apparatus in a secondary network periodically or irregularly senses frequency resources that are not used in a primary network to recognize available frequency resources. Accordingly, the communication apparatus can receive and/or transmit a signal using the recognized available frequency resources. In this instance, however, the primary network has a priority with respect to the available frequency resources.
Furthermore, according to the CR technology, a transmitter of the primary network can transmit a data signal and a pilot signal. When power of the pilot signal is low, the secondary network may not recognize that the primary network is using the available frequency resources. Conversely, when the power of pilot signal is high, power of the data signal of the primary network may be low as a result.
When the primary network cannot recognize that the secondary network is using an available frequency resource, a signal of the primary network may collide with a signal of the secondary network. Moreover, when the power of the data signal of the primary network is insignificant or low, the primary network cannot increase a channel capacity. Accordingly, a technology to control power of a pilot signal is needed.